2,5-furandicarboxylic acid (FDCA) is a monomeric compound which can be applied in the production of polyesters which have a tremendous economic impact. A very important compound in the field is polyethyleneterephthalate (PET) which is produced from terephthalic acid (PTA) and ethylene glycol. FDCA may substitute for PTA in the polyester PET in which case polyethylenefurandicarboxylate (PEF) results. PEF has a good potential in replacing PET in the large polyester market. Not only because it has superior properties when compared to PET, but also because it can be derived from renewable feedstocks. FDCA can be produced from sugars either chemically (De Jong et al 2012. In: Biobased Monomers, Polymers, and Materials; Smith, P., et al.; ACS Symposium Series; American Chemical Society: Washington, D.C.) or in a combined chemical-biological route (Wiercks et al 2011. Appl Microbiol Biotechnol 92:1095-1105). In the latter case, a monomeric sugar such as glucose or fructose is chemically transformed into 5-(hydroxymethyl)-2-furaldehyde (HMF) which subsequently can be oxidized by enzymes into FDCA.
A biological route for producing FDCA from HMF has been developed based on the isolation of the HMF-degrading strain of Cupriavidus basilensis HMF14 (Wierckx et al 2010. Microbial Technology 3:336-343). A cluster of genes encoding enzymes involved in the HMF degradation route in C. basilensis HMF14 was identified and relevant genes were heterologously expressed in a Pseudomonas putida strain (Koopman et al 2010. PNAS 107:4919-4924) which thereby acquired the ability to metabolize HMF. The first oxidative step in the degradation route involved the formation of 5-(hydroxymethyl)-2-furoic acid (HMFCA) which in turn was oxidized into 5-formyl-2-furoic acid (FFA) and further into FDCA. In subsequent work (Koopman et al 2010. Bioresource Technology 101:6291-6296; and WO 2011/026913), only the hmfH gene of C. basilensis HMF14 that encodes the enzyme HMF oxidoreductase was introduced into P. putida. The oxidoreductase acts as an oxidase mainly at HMFCA, but it also may oxidize HMF or FFA. The heterologous expression of only the hmfH gene enables P. putida to produce FDCA from HMF. In further optimization work (Wierckx et al 2011, supra; and WO 2012/064195), two additional genes were expressed in P. putida that encode for an HMFCA transporter and for an aldehyde dehydrogenase with unknown specificity, respectively.
However, the oxidase-catalysed route for the production of FDCA from HMF has several inherent disadvantages as compared to a dehydrogenase-catalysed route, which include at least the production of toxic H2O2, the lack of energy gain from the oxidative step and the poor affinity for O2 and associated high oxygen demand of the system. It is therefore an object of the present invention to address these disadvantages by providing means and methods for a novel dehydrogenase-catalysed route for the production of FDCA from furanic precursors such as HMF, as well as providing means and methods for using a novel HMFCA transporter in such processes.